Disk drive devices which employ a variety of recording disks, such as optical disks, magneto-optical disks, or flexible magnetic disks, are known in the art, and among these, hard disk drives (HDD) are widely used as recording devices for computers, and are also used in many items of electronic equipment, such as video recording/reproduction devices or car navigation systems.
The magnetic disks, which are used in HDDs, comprise a plurality of data tracks and a plurality of servo tracks. One or more data sectors containing user data are recorded in each data track. Each servo track comprises address information. The servo tracks consist of a plurality of items of servo data which are arranged at intervals in the circumferential direction, and one or more data sectors are recorded between each item of servo data. A head element unit is able to write data to the data sectors or read data from the data sectors by accessing the required data sector in accordance with the address information of the servo data.
The head element unit is formed on a slider which is attached on top of a suspension of an actuator. The suspension and head-slider assembly is known as the head gimbal assembly (HGA). Furthermore, the actuator and head-slider assembly is known as the head-slider assembly (HSA). The pressure created by the viscosity of the air between the slider floating surface opposite the magnetic disk and the rotating magnetic disk is balanced with the pressured applied in the direction of the magnetic disk by the suspension so that the head-slider can float above the magnetic disk. The actuator is pivoted about a pivot shaft, whereby the head-slider is moved to the intended track and is also positioned above said track.
There is now a need for improved accuracy in the positioning of the head-slider as the TPI (tracks per inch) increases in magnetic disks. However, a limit has already been reached in terms of the positioning accuracy with which the actuator is driven by the voice coil motor.